NAME
viomb —
VirtIO memory ballooning
driver
SYNOPSIS
virtio* at pci? dev ? function ?
viomb* at virtio?
DESCRIPTION
virtio(4) defines an interface for efficient, standard, and extensible I/O between the hypervisor and the virtual machine. Theviomb driver supports the virtio-compliant memory
ballooning device.
Memory ballooning works as follows:
- The host operator requests a guest to return some amount of memory to the host (via e.g. Qemu monitor balloon command).
- The hypervisor sends the request via VirtIO memory ballooning device.
- The guest
viombdriver requests allocation of that amount of physical memory from the NetBSD memory management system. - The
viombdevice tells the hypervisor the guest physical memory address of the allocated memory via VirtIO memory ballooning device.
The sysctl node hw.viomb.npages shows the
requested number of memory pages to return to the hypervisor, while
hw.viomb.actual shows the actual number of memory
pages that are already returned to the hypervisor.
SEE ALSO
Rusty Russell, IBM Corporation, Virtio PCI Card Specification, http://ozlabs.org/~rusty/virtio-spec/.
HISTORY
The viomb device driver appeared in
NetBSD 6.0.
BUGS
The userland interface should be same as the Xen ballooning device.